You say your main concern is cost and you were suggested to get a 2tb thunderbolt drive that costs $900. You can get an 8tb sata ssd for the under $800 right now. Do not let anyone tell you that no one can do it better than Apple because if you look at an Apple ssd, guess what it says on it: Samsung. These are all just x86 machines with software locks on them (aside from the T2) you just need to figure out what and where to patch for yourself; making a Mac do what you need it to do whether or not Apple “allows” it is not for the faint of heart and that’s why we come to iFixit, not for out of the box solutions. keep hacking away and have fun.